Can Compact Lasers Have An Impact For Onychomycosis?

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What You Should Know About The Science Behind Lasers

The main characteristic of the laser’s electromagnetic waves is the wavelength, which is measured in nanometers. For clinical purposes, a second characteristic of lasers that is very relevant is the average power, which is measured in watts.

As with many other types of waves, laser energy can be reflected, transmitted, absorbed, scattered or refracted. A chemical reaction occurs only when cells absorb light. When absorbed by cells, laser light converts into either heat or biochemical energy. Different wavelengths affect the conversion in different proportions. For example, a wavelength such as 1,064 nm will interact with soft tissues to optimally convert into heat for an ablative effect. Another wavelength such as 2,400 nm will interact more effectively with bone. The amount of light energy that converts into biochemical energy is minimal, which ensures maximum ablative efficiency.

Most human tissues are poor absorbers of lasers with wavelengths of 600 nm and 1000 nm, which would produce less conversion to heat and would allow for deeper tissue penetration. As all of the therapeutic lasers in the market today have wavelengths in the therapeutic window (between 600 and 1,000 nm), they all meet the first criterion to be able to deliver light energy into the tissue. It is for these reasons that the Nexus line of lasers have either 810 nm or 980 nm wavelengths.

The power of the laser device is the second factor for effective delivery of light energy into the target tissue for absorption. A laser device could have the appropriate wavelength and still be unable to drive the light energy to the tissue that needs treatment. This is not unlike standard radiography equipment. Therapeutic lasers need to have the appropriate wavelength and power to produce the desired therapeutic effects in the tissue one is treating.

Numerous researchers have stated that therapeutic lasers do not provide positive clinical effects and provide no negative side effects.2,3 By analyzing the articles that reported no clinical effects, one easily finds a pattern: most of these researchers in these studies used low doses in their clinical trials and this was usually due to using a low-powered laser instrument.

The dose in laser therapy is the amount of light energy, measured in joules, delivered to a given unit area during a treatment session. Simply stated, 1 J of energy is delivered by a 1-W laser emitter for one second or other combinations of the two parameters laser power (in watts) and time (in seconds). Therefore, energy density is the energy per cm2 (J/cm2).

Power density is the amount of power (watts) delivered to 1 cm2 of tissue area. One determines this by the size of the treatment applicator and the emitted power. One can conclude that the larger the applicator, the lower the power density because the treated area is larger. Likewise, the lower the average power of the device, the lower the power density because the beam is not as intense. The same results are present in lasers with multiple diodes with the same average power. The power density of a laser with multiple diodes is lower than lasers with a single diode. Research has determined that power density plays a major role in the therapeutic process.4

Tuner and Hode demonstrated that the optimum dose necessary to obtain therapeutic effects at the treated tissue should be at least 4 J per cm2.5 To estimate the energy reaching the target tissue, one must consider the depth of the treated area and the composition of the layers of tissues between the laser applicator and the treated tissue.

A typical laser device in the United States emits approximately 7 milliwatts of power using a 635-nm laser diode (red light). As a comparison, a laser pointer commonly used for presentations typically emits 3 to 5 milliwatts of power in the 660-nm range. On a per-milliwatt basis, the cost comparison between them is staggering. In terms of energy density, the same typical therapeutic laser, as reported by the manufacturer, delivers 0.0002 to 0.0003 J per minute/cm2. As an illustrative example, to deliver the minimum necessary energy at a skin target tissue (no tissue penetration needed) to obtain therapeutic value would take approximately 2,500 minutes.

Author(s): 
David Zuckerman, DPM, FACFAS

   The Nexus family of lasers comes in powers of 7 W, 10 W, 15 W, 20 W, 30 W and 60 W with wavelengths within the therapeutic window. Furthermore, Nexus lasers are all designed with a single diode to ensure the highest power density.

   Another laser of note is the compact Q-Clear laser (Light Age Technology), a Q-switched laser that works on cavitation rather than direct heating of the dermis. Accordingly, the laser does not cause the heat and pain that were characteristic of previous lasers. It is fast and affordable for the patient.

   The Q-Clear laser system is safer and more effective in treating dystrophic nails, particularly those due to onychomycosis, in comparison to previously available methods. In clinical studies, it has demonstrated a 97 percent success rate in providing significant clearance of affected toenails without any significant side effects and without causing pain.6 In addition, the average clearance of the toenail was 57 percent across the board. In these studies, most toenails achieved substantial or complete improvement after only a single treatment. These results occurred using a simple treatment protocol, which generally consisted of laser treatment without the application of adjunctive topical therapies or use of any anesthetic agents, and took less than five minutes per foot. Due to the efficacy, speed and lack of disposables, there are significantly reduced treatment costs that have helping to expand the availability of the treatment.

   The Q-Clear is a Nd:YAG laser system with certain unique properties that differentiate it from lasers that have been used previously in podiatry. Nd:YAG lasers themselves are relatively new in podiatry and the FDA has cleared the laser only within the last year for “the temporary increase of clear nail in patients with onychomycosis,” making Q-Clear only the third such laser system to be FDA cleared for this application.

   The Q-Clear laser system delivers sufficiently high pulse energies in spatial and temporal pulse formats. These formats were designed to provide the heating and photomechanical disruption needed to penetrate and kill the fungal colonies without causing pain or adversely affecting the surrounding tissue. In addition, the cost of treatment (for everything related to the laser system) is under $10 per fully treated foot.

Pertinent Insights On Q-Switching And Nd:YAG Technology

Nd:YAG laser systems provide fundamental light output in the near infrared region of the spectrum. Most commonly, the output is at a wavelength of 1,064 nm, slightly outside of the range of visible light (nominally 400 to 800 nm, violet to deep red). The output of these laser systems can occur in either a continuous wave or in a pulsed format. It is sometimes “frequency doubled” by the nonlinear process called second harmonic generation to the green laser wavelength of 532 nm.

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Dr. Eric Bornsteinsays: November 18, 2011 at 1:24 pm

There are two major factors that need to be taken into account when discussing lasers and podiatric therapeutic indications that are missing here for this discussion of onychomycosis.

First, the perimeter of a human nail is made up of three right angles (a three sided square) with a rounded edge at the proximal tip.

For an area like this to be correctly and adequately irradiated with laser energy, there needs to be a Uniform Beam Dosimetry across the entire diameter of the treatment spot. Only this will deliver a uniform therapeutic dose across the entire area of a nail being treated. The only device that accomplishes this task is the Noveon Podiatric Laser.

A uniform beam dosimetry is also known as a “flat-top projection” of laser energy. This is in contrast to a “Gaussian projection," which contains a hot spot and is non-uniform in its energy delivery, which is the delivery mechanism of most commercial near-IR devices.

Also, the Noveon treatment spot geometry is a larger flat-top circle. Hence with this difference in beam geometry, there is always a small area of paronychial tissue surrounding the nail that is included within the treatment area spot size. With distal lateral onychomycosis, this is necessary to help prevent re-infection.

Second, one should carefully review the peer-reviewed literature describing IRB approved human clinical trials before making any treatment decisions with lasers for their patients. In this way, good evidence based medicine can be practiced for potential patients. The largest body of this literature can be found below.

When a laser company tells you the data "is on file" and not published, one should ask the question why? If they do not have data, one should ask "Then how do I know what amount of energy to use?" and "Who has evaluated the use of this energy?"

Dr. Eric Bornstein
Chief Science Officer
Nomir Medical Technologies

Landsman, A. et al. (2010) Treatment of Mild, Moderate and Severe Onychomycosis Using 870nm and 930nm Light Exposure J. of the Am. Pod. Med. Assoc. 2010 100:166-177

Bornstein E., S. Gridley, and P. Wegender (2010) Photodamage to Multidrug-resistant Gram-positive and Gram-negative Bacteria by 870 nm/930 nm Light Potentiates Erythromycin, Tetracycline and Ciprofloxacin. Photochem. and Photobiol Volume 86 Issue 3, Pages 617 - 627

Bornstein E.S. (2009) A Review of current research in light-based technologies for treatment of podiatric infectious disease states. J. of the Am. Pod. Med. Assoc. 99 (4), 348-352.

Bornstein E., W. Hermans, S. Gridley, and J. Manni (2009) Near infrared Photo-inactivation of bacteria and fungi at physiologic temperatures. Photochem. and Photobiol. 85, 1364–1374

Bornstein E.S. (2009) Treatment of onychomycosis using the noveon® dual-wavelength laser. FDA Pivotal Study data presented at Council for Nail Disorders 13th Annual Meeting, San Francisco, CA, March 5, 2009.

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